As part of a continuing study of intestinal motility, myogenic rhythmicity of smooth muscle is examined by several methods of electrical recording. Amplitude of "slow waves" depends on rate of sodium-potassium transport but frequency is modulated by other events. Calcium is critical in frequency control and measurements are to be made of both calcium and sodium fluxes, of Ca effects on Na ATPase, and of intracellular concentrations of free calcium. Correlation will be obtained of cellular metabolism as reflected by NADH-NAD ratio with fluxes and concentrations of calcium. A scheme for the role of Ca-Na interactions in the generation of rhythmicity is being developed. An animal model of obstructive ileus provides large smooth muscle fibers which will be used for study of mechanisms of generation of slow electrical waves.